The invention relates to a device for the chucking of tubular winding cores, and particularly of cores carrying paper webs or webs of similar material, wherein chucking segments forming a cylindrical surface are radially positioned by means of a core trunnion having an equilateral polygonal cross section, each of said chucking segments bearing on an individual surface of said trunnion through a support member having a rounded profile and producing a line contact.
Expandable chucks of this type are inserted from both sides into the axial openings of winding cores and fixed therein by interlocking and operative engagement to prevent slippage between the chucks and the core as the web is being wound onto it or unwound from it. To provide a good grip, the chuck is seated in a segmented outer ring. In their normal position, the partly cylindrical chucking segments are forced radially inward by springs to abut on one another. The chuck is inserted in the core tube with the chucking segments in that position for interlocking engagement therewith. In winding the web onto the core or unwinding it therefrom, and also in braking the core, there is increased likelihood of slippage between the chucks and the core. The preclude this, the chucks are expanded in that the chucking segments are spread radially outward, by the effect of the forces generated by the web tension or the braking action, to provide in addition to the interlocking engagement also operative engagement with the core tube.
In a prior-art device of the type outlined above and shown in (German patent application DOS No. 22 11 518, this is accomplished in that the chucking segments upon the occurrence of a tangential force at the chuck are deflected from their normal position, imposed on them by the spring. As the support member disposed on the chucking segment slides along the surface of the core trunnion, it causes the chucking segment on which the force is acting to expand radially and so to become lodged more securely in the winding core.
It has now been found that this design has the drawback that in practice the only chucking segment that is deflected is the one on which the web-tension or braking force is acting. The other chucking segments distributed over the circumference of the chuck are not deflected. This leads to increased abrasion at the inner circumference of the winding core, with the abraded particles settling between the chucking segments, thus impairing their ability to move, with the result that ultimately the chucking segments will be unable to return into their normal position and the chuck then cannot readily be withdrawn from the winding core. In any event, such fouling will call for frequent cleaning of the chucks if they are to be kept in good working condition.